Granny Gears Too Low..Solutions ?

[kwmech]

Is there a tag on either the front or rear diff covers? It will be under one of the bolts holding the cover on

[Mike C]

Should be easy to get a set of 1/2 ton 4x4 axles with either 3.07 or 3.73 gears from a 70's truck and swap 'em in. Get disc brakes that way too.
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[franken]

A few ideas:
The diffs need the oil changed or have almost none anyway. Drop the $20 and pull a cover to find out for sure. The ratio is stamped on the ring gear.
With a 4x4, swapping diffs isn't so simple because doners (73+) don't have the right spring mount spacing. I'm guessing this is a half ton. So a 2x diff swap is impractical for $1k.
Get a tach and find out what the engine is turning in reality. This is a 46 year old truck. It isn't like a new vehicle and what its acting like is normal for the time.
What engine is in it? A 6 or original 6 truck would have a lower ratio than a V8.
I'm pretty sure the 69 trucks had a married TC, so a trans swap to OD is impractical for $1k.

[franken]

Originally Posted by Mike C

Should be easy to get a set of 1/2 ton 4x4 axles with either 3.07 or 3.73 gears from a 70's truck and swap 'em in. Get disc brakes that way too.
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Spring perches were on different centers and one shock mount is on the wrong side.

[Mike C]

So it doesn't bolt right in. Neither does a gear set or a differential set itself up.

I have 3/4 ton axles from an '86 in my '72. I removed and reused the donors spring perches. I used the OEM shock mounts from my original axle. No biggee. And even if you had to pay to have that done, no more than a couple $100.

I paid $300 for the Suburban with a broken motor. I bought another '83 3/4 ton sub for $200 and a '76 Blazer for $300. They are out there, and they are cheap. If you can't do this swap for $1000 you didn't try. 1/2 ton axles are out there it seems all over because 3/4 ton such a better choice IMO but if driveability is the goal, the 1/2 tons will work great.

If you have the whole thing apart anyway, you could also swap the gear set into the existing 12 bolt housing (assuming you get a '73-'79 donor and not an 8.5" 10 bolt truck). Either way, the truck will be much more driveable and safer with discs.

[RanchTruck]

A tachometer to see what actual RPM the engine is turning would be the first step. Converting to a clutched cooling fan would greatly reduce the roar. Seeing on the tach that the engine isn't actually screaming, and not hearing the fan roaring, may be all you need to feel OK with driving it at highway speeds.

['68OrangeSunshine]

Benbloom -- a Rockwell T-221 transfer case is unusual in a '69 K/10. I thought 1968 was the [first and-] last year for an SM 465/T221 set up. (With GMC and Canadian hold-outs until they ran out in '69.) With a Marin County location, the most statistically probable origin for a GM truck would be Fremont [code Z] across the Bay. But then we all know how these rigs get around.
Also after 40+ years, who knows what a PO may have cobbled together, just to get back on the road. You could even have the SM420 4-speed, also a Granny Gear tranny, but with even lower ranges in 1-2-3. Also you never use 1st [Granny] unless you have a full load of riprap in the bed. SM420s last production year was 1967.
The VIN would be helpful. Or a pic of the SPID. You can use X's for the last five numbers, if you're security conscious.

That being said, I have heard the Rockwell T221 was very noisy in its own right, even on a good day. I have a core SM465/T221 [that was misrepresented to me as a 205 by an long-gone junkie] I thought 1968 was the only year for that combo. I hear it's a strong TC but replacement parts are hard to get now.
One more thing, make sure the gear oil levels are up to spec. SAE 90 GL-5 will work. They get loud if the levels are too low. [Just before they burn out.]

GASoline71-- I remember premium ARCO selling for .25/GAL in Hollywood in 1969. We would've rioted if it was as high as .40!

[benbloom]

'68OrangeSunshine- i usually start in 2nd, how do i figure out what trans i have? it is very noisy, the thing is an absolute gear. il try to get the vin number on here asap!
thanks everyone for the help, i figure il probably just live with the very low gears, and no, its not that I'm just not used to the old trucks, driving my friends k10s with the automatic tranny there is a very noticeable difference. again, thanks everyone, il get the vin asap

['68OrangeSunshine]

Originally Posted by benbloom

'68OrangeSunshine- i usually start in 2nd, how do i figure out what trans i have? it is very noisy, the thing is an absolute gear. il try to get the vin number on here asap!
thanks everyone for the help, i figure il probably just live with the very low gears, and no, its not that I'm just not used to the old trucks, driving my friends k10s with the automatic tranny there is a very noticeable difference. again, thanks everyone, il get the vin asap

Both the SM 420 and the SM 465 have the compound low 1st gears.
The only way to tell 'em apart is by the Reverse Gear position:
420-Reverse is toward you and back [left of center of #2 on the gearshift pattern]
465- Reverse is away from you and back, off center from #4.
1-2-3-4 Are in standard H pattern.
You might also look on the SPID for a transmission RPO code. It may be listed as "SynchroMesh Transmission'', [Which they both are.]
<<M20 4 Speed>> may be a 465. This is all from memory.

[benbloom]

reverse is to the right and towards the bench ?

['68OrangeSunshine]

Originally Posted by benbloom

reverse is to the right and towards the bench ?

Yeah. On the 465.

[dazza]

My K10 (72 w/ sm465/np205) isn't quite back together yet to compare, but if you're out near either Discovery Bay or in SF with the truck, I'd be happy to at least take a ride with you and tell you if it sounds normal.
I was looking at adding a Gear Vendors OD and after a lot of research I found a guy up in Sac that rebuilt and sold them, he told me with my ratio (3.07) it wouldn't do me any good.

[Tony]

I have a 68 K10 with the Rockwell 221 and 4 speed.. I thought 68 was the last year for the Rockwell?
1968 Chevy K10 factory information shows the standard axle gear ration as 3.73 with no optional ratios available as original equipment. I will assume 69 is the same but of course the gears might have been changed over the years.
3.73's with typical 235/15 tires is around 2600-2700 rpm at 60 mph. While not the 1400 rpm of a new truck it's not all that much engine speed and you can cruise all day at 65 ...
My 68 with a 250 sounds busy at 60 mph but I pay no attention to and drive on....It's an old truck with minimal or no sound deadening...Not a 2015 Silverado